DESCRIPTION Prior research has found that cerebellar blood volume as measured with Dynamic Susceptibility Contrast MRI is higher in the cerebellum of schizophrenic patients and lower in bipolar patients compared to normals. The reasons for these significant differences is unclear. The literature suggest there may be degeneration or mal-development of the cerebellum in schizophrenic and bipolar patients. First, high resolution structural T1*- weighted images coupled with segmentation and C-D reconstruction software will provide a measure of morphometric tissue changes in individual cerebellar lobules. Second, DC MRI will be used to measure cerebellar blood volume during rest and challenge tasks. This measure signals changes in vascular beds due to a disease state. Lasts. Blood- Oxygen-Level Dependent functional MRI techniques utilizing cognitive challenge paradigms elicits information about the metabolic state of cerebellar tissue. Of particular interest is whether these measures of neuronal integrity correlate with clinical measures of psychosis and neuropsychological test scores. The details of these measurements will provide information about the specific dysregulation of the functional components of the cerebellum.